BMR Rear Suspension Install - Strong Arm

Take wheelhop and unpredictability out of your second-gen’s rear suspension with this torque-arm/Watt’s-link setup from BMR Suspension

Suspension technology has come a long way in the nearly 42 years that have passed since the '70 Camaro first hit showroom floors. Spring and shock developments, tire advancements, improved brake technology, and overall design progression have brought factory handling to an all-time high. While the Z28 was top dog for handling then, a V-6 2011 Camaro today could easily out-maneuver any of its ancestors.

Thanks to the aftermarket though, those classic Camaros don't have to be left in the dust by the factory behemoths rolling off the assembly line in Canada.

Back in the May 2009 issue of Super Chevy, we covered the install of BMR's torque-arm/Watt's-link suspension system for first-generation Camaros. Now with the design proven on road courses and dragstrips, BMR has adapted it to help improve the rear suspension and handling of the second-generation F-body.

While leaf springs aren't bad performers by any means, they do have wheelhop problems under hard launches and suspension binding that occurs during hard cornering. A torque-arm suspension eliminates these problems. The main arm that goes from the rearend up to the transmission features a slider on the transmission end that allows the arm to slide fore and aft along with rotating as the suspension goes through its range of motion. This allows the car's handling to be controlled more by the coilover shocks, tires, and in this design's case, the Watt's-link bars. A Watt's-link system controls the lateral movement of the car's rear while also allowing for the side-to-side adjustment/position of the rear for better handling depending on the track and conditions. Overall, the BMR design keeps the rear stable but allows for independent articulation of each rear wheel, as opposed to a four-link design, which keeps the rear wheels articulating together.

Here are some of the adjustability features of our subject BMR torque-arm/Watt's-link kit:

Three-position ride-height adjustability plus coilover adjustability: Ride height should never be adjusted with the coilover itself, according to BMR. Contrary to popular belief, the spring collar on a coilover is designed to adjust spring preload, not ride height. BMR torque-arm kits have three coilover mounting positions spaced 1 inch apart for adjusting ride height.

Five-position roll-center height adjustability on the GM 10/12-bolt kits and seven-position roll-center height adjustability on the 9-inch kit: The roll center is the axis of rotation for the car when the body rotates left to right. Front and rear roll centers are typically not adjustable. By providing an adjustable rear roll-center height, the user can fine-tune the vehicle's roll axis for optimal handling characteristics.

Lateral Watt's-link adjustability: The Watt's linkages are adjustable in length to allow fine-tuning of the lateral rearend position in the chassis.

Now that you know the basics, follow along as we show you how easy it is to install this system in a second-generation Camaro.

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1 First up is removing the two rear bolts holding the front subframe assembly to the body, and the bushings. New longer bolts and polyurethane bushings are included with the BMR kit.

2 Here’s the whole BMR torque-arm/Watt’s-link kit, sans the included nuts and bolts. It should be noted at the outset that use of this kit will require a custom-made exhaust system.

3 Replacing the factory rubber bushings are these polyurethane pieces. If your car hasn’t had its bushings replaced before, it might not be a bad idea to go ahead and replace all of the front subframe bushings and upgrade to either polyurethane or polygraphite. You’d be amazed at the difference they make, not to mention their durability.

4 The mounting ears for the forward torque-arm crossmember mount on top of the factory subframe as seen in this photo. Once they and their bushings are in place, install (but don’t tighten) the new subframe bolts to hold them steady.

5 Next, slide the crossmember into position. Because these parts are powdercoated, the fit might be a bit tight, necessitating the use of a rubber mallet to coax the crossmember into position.

6 With the crossmember bolted in, you can tighten up the subframe bolts and lock the mounting ears in place.

7 Next up is the mounting plate for the rear torque-arm mount and Watt’s-link system. It mounts using four studs that screw into the rearend cover bolt holes. The kit also includes gaskets, one for each side of the mounting plate.

8 The BMR kit will work with most 12-bolt covers like this aftermarket piece. Secure the cover and you’re ready to move on.

9 The forward torque-arm yoke bolts onto the crossmember installed earlier. It has a greaseable, high-durometer polyurethane bushing for long life and bind-free movement.

16 This battleship-grade monster serves as the rearend mount for the lower control arm and the lower mounting point for the coilover shocks. It features three different mounting holes for the control arms and the shocks, providing for numerous adjustments to suit any handling needs.

17 The control arms bolt right in place, featuring greaseable polyurethane bushings up front and adjustable Heim joints in back.

18 The next piece to install is the upper shock/Watt’s-link bar mount. The kit comes with two self-tapping sheetmetal screws to hold the mount in place while you install its permanent mounts.

10 Here, the torque arm is being slid into place. The torque arm alone provides an enormous amount of stability for the rear suspension that will improve cornering and other handling. It also has a Delrin-bushed front slider for the mounting yoke.

11 The rest of the torque-arm mount consists of these side bars, which bolt in place and also help to support the Watt’s-link system.

12 Time for the leaf springs to come out. Make sure the rearend is fully supported, then unbolt the spring shackles.

19 The only drilling you have to do for installing the BMR kit is enlarging two holes on each side of the rear subframe. This is easily done with a large 1/2-inch drill bit, followed by a Unibit to get the hole diameter just right.

20 The reason for the large holes is so these bushings/reinforcements can fit inside the framerail to keep it from collapsing once the upper mount is secured properly.

21 With the outside mounting tab and bushings in place, the bolts are tightened. Once complete, you can remove the two self-tapping screws that temporarily held the mount in position.

13 Take care when removing the front leaf-spring mounts from the body, as they’ll be reused with the new BMR lower control arms.

14 The factory leaf-spring mounts attach to the front of the new lower control arms.

15 Because the factory system only used U-bolts on the outside of the spring, you’re going to have to move/adjust the brake hard-line on the axletube to clear the U-bolts for the new mounts that secure the rear to the lower control arms.

22 The central Watt’s-link mount/pivot installs like this. If you’re ever curious about a Watt’s-link system, just look underneath the rearend of any 2003-up Ford Crown Victoria or Mercury Grand Marquis. These cars have a Watt’s-link suspension from the factory.

23 The new coilover shocks go in place and will handle not only height adjustment with their different mounting positions but also control most of the car’s handling because of the increased stability of the rear.

24 The center link/pivot point for the Watt’s-link bars can be adjustable to several different heights, all depending on your handling needs because of the track/environment you’re in. When installing the kit, the best initial adjustment is to mount the pivot point in the lowest pair of holes.

28 To set your ride height and make sure both sides are even, use a tape measure and measure from the center of the wheel to the bottom of the fender’s lip on both sides. If the measurements aren’t the same, then pick which height you want and adjust the other shock accordingly to equal them out.

29 Raising or lowering the rear ride height is simply a matter of changing the lower mounting position of the coilover. The BMR kit allows for three different mounting positions. Each mounting position is spaced 1 inch apart.

30 Next up is the lateral adjustment. Using a plumb bob, measure from the rim of the wheel to the plumb bob line on both sides. If both measurements aren’t the same, then the Watt’s-link bars need to be lengthened/shortened to even out both measurements.

25 The Watt’s-link bars feature the same greaseable bushings as the control arms for bind-free operation and durability.

26 With the bars in place, it’s time to set the rearend’s pinion angle before tightening up all the mounting bolts. In this instance, the pinion angle was set at 4 degrees. Further adjustments are easily made and all depend on your car’s exact setup.

27 Here’s the whole kit, installed and ready for final height and lateral adjustment before seeing the track.